1. Field of the Invention
The present invention relates to a capped collet for holding a tool, which is inserted into a tool holder mounted to a main spindle of, for example, a machine tool, and also relates to a cap attached to the collet.
2. Description of the Related Art
In tool machines such as lathes, drilling machines, or milling machines, collets have been used as a part of holders for holding tools such as drills or end mills. This type of collet generally comprises a collet body, into which a shank of the tool is inserted, and slots formed in the collet body.
It is necessary to cool these tools continuously in order to suppress heat generated at the time of processing (cutting) works. The tools are sometimes lubricated in order to obtain better workability. As a method for such cooling and lubrication, a cutting fluid (cooling fluid) such as a water soluble coolant, oil, mist, or semi-dry fluid is supplied to the tool. As an example of the method for supplying the cutting fluid to a tool, a tool with a through hole extending in its lengthwise direction is used and the tool is cooled by causing the cutting fluid to flow through the through hole. This method is intended to supply the cutting fluid to the through hole in the tool efficiently, for example, by providing a weir material at a specified position of the slot in order to prevent the cutting fluid from flowing out from the slot formed in the collet body, or by providing a sealing mechanism on the base-end side (opposite to the tool-inserting side) of the collet body.
When a tool is used which has no through hole described above, there is a general method for cooling the tool by supplying the cutting fluid between the collet and the tool held by the collet by utilizing the slot formed in the collet body.
When the method of cooling the tool by causing the cutting fluid to flow through the through hole of the tool is employed, it may be burdensome to insert the weir material into the slot. There is also a fear that the weir material may easily come off the slot when the collet body is contracted to hold the tool. On the other hand, the collet with the sealing mechanism on the base-end side of the collet body has the drawback that it is impossible to adopt various methods for supplying the cutting fluid according to the type of the tool.
In the method of supplying the cutting fluid to the tool by utilizing the slot formed in the collet body, a cross-sectional area of the slot in its radial direction changes depending on the diameter of the tool to be inserted into the collet body and, therefore, the speed of the cutting fluid changes accordingly. As a result, there is a fear that it may become difficult to always supply the cutting fluid efficiently to a desired position of the tool. Particularly, there is a fear that even if the cutting fluid is supplied at high pressure, the cutting fluid may be dispersed due to centrifugal force at the time of high-speed rotation before it reaches the cutting edge of the tool.
The present invention is aimed at improving the conventional collets and the caps attached to such collets as described above. It is an object of this invention to provide a capped collet and a cap attached to the collet, which can supply the cooling fluid to the tool efficiently at an appropriate flow velocity, with an appropriate flow rate, and in an appropriate flow direction, depending on the type of the tool held by the collet, thereby enabling satisfactory cooling.
In order to achieve this object, this invention provides a capped collet for holding a tool by inserting a shank of the tool in a center hole of the collet mounted in a tool holder for supplying a fluid to the tool, the collet comprising: a collet body for inserting the shank of the tool therein; a cap mounted on the tool-inserting side of the collet body in an attachable and detachable manner, for allowing the tool to pierce therethrough; and a sealing member located between the tool holder and the cap, for hermetically sealing a space between them; wherein the collet body has a slot formed at least from the tool-inserting side thereof, and a second coupling element formed in the tool-inserting side thereof to couple with the cap; and wherein the cap has a first coupling element for coupling with the second coupling element of the collet, and a cover for covering the tool-inserting end face of the collet body.
With the collet having this structure, it is possible to attach and remove the cap and to hermetically seal a space between the tool holder and the cap. Accordingly, it is possible to enhance general versatility by replacing the cap with another cap in the shape which satisfies various conditions such as the oil supply pattern of the tool, and desired flow rate, flow velocity, and flow direction of the cooling fluid.
The second coupling element can comprise an annular groove formed around the outer surface of the collet body on its tool-inserting side.
The first coupling element can comprise an annular projection formed around the inner surface of the cap, for coupling with the annular groove formed in the collet body.
The capped collet of this invention can cause the fluid to flow out from a gap formed between the cover of the cap and the tool. Accordingly, it is possible to arbitrarily decide, for example, the flow rate, flow velocity, and flow direction of the fluid by adjusting the size, shape, and other factors of the gap.
Concerning the capped collet of this invention, the cover of the cap can have a fluid path formed therein for causing the fluid to flow out. In this case, it is possible to arbitrarily decide, for example, the flow rate, flow velocity, and flow direction of the fluid by adjusting the formed position, size, shape, and other factors of the fluid path.
Moreover, the capped collet of this invention further comprises a sealing member for hermetically sealing a space between the cover of the cap and the tool, and the fluid can be made to flow out from a through hole formed therein. Accordingly, it is possible to cause the fluid to flow out efficiently from the through hole formed in the tool.
The sealing member which hermetically seals the space between the cover of the cap and the tool can cause the space to be hermetically sealed more tightly by means of the pressure of the fluid. Accordingly, even when a high-pressure fluid is supplied, it is possible to realize high sealability, thereby enabling efficient supply of the fluid from the through hole of the tool.
The capped collet of this invention may have a straight collet or a tapered collet.
Moreover, this invention provides a cap attached in an attachable and detachable manner to the tool-inserting side of a collet which holds a tool by inserting a shank of the tool in its center hole and which is mounted in a tool holder for supplying a fluid to the tool, and the cap comprises: a first coupling element for coupling with a second coupling element of the collet; a cover for covering the end face of the collet on the tool-inserting side; and a sealing member located between the tool holder and the cap, for hermetically sealing a space between them.
The cap having the above-described structure can be removed from the collet. Accordingly, it is possible to enhance general versatility of the collet by using the cap in the shape which satisfies various conditions such as the oil supply pattern of the tool, and desired flow rate, flow velocity, and flow direction of the cooling fluid.
The first coupling element can comprise an annular projection formed around the inner surface of the cap, for coupling with an annular groove formed around the outer surface of the collet.
The cap of this invention can cause the fluid to flow out from a gap formed between the cover and the tool.
Moreover, the cap of this invention can be structured in such a manner that the cover has a fluid path formed therein for causing the fluid to flow out.
Furthermore, the cap of this invention further comprises a sealing member for hermetically sealing a space between the cover and the tool, and the cap can be structured so as to cause the fluid to flow out from a through hole formed in the tool.
The sealing member which hermetically seals a space between the cover and the tool can be structured so as to cause the space to be hermetically sealed more tightly by means of the pressure of the fluid.